Summary

When Zika virus infects pregnant women, it can pass to the fetus and attack developing brain cells. In the most well-known symptom, the infection leaves the baby with an unusually small head, a condition called microcephaly. Now, case reports make it increasingly clear that babies infected in utero also have problems in their eyes, ears, limbs, and perhaps other organs. Earlier this month the World Health Organization announced that it is launching an effort to characterize what doctors are now calling Zika congenital syndrome. Experts will meet in July in Recife, Brazil, to develop a preliminary definition of the syndrome and guidelines for doctors screening infants that may have been infected before birth. Animal- and cell-based studies have shown that Zika virus readily infects the cells of the nervous system, and it seems to be especially dangerous for rapidly dividing stem cells. In some cases the damage is so extensive that the skull has filled mostly with fluid, with very little brain tissue. Those babies die shortly after birth. Other infected infants may have only mild brain damage that will not be apparent until learning disabilities or other problems show up years later. Researchers are setting up long-term studies to follow pregnant women and their babies to better understand the risk the virus poses.